If that's what they did, seems like a very cheap way to collect the names/social media profiles/email addresses of all the people discussing the puzzle. Now somebody has a list of at least several thousand profiles who've shared tweets regarding it, sent emails to the info@ address, and can collate it against other lists of persons or pseudonyms interested in both cryptocurrency and this sort of online puzzle.

You are devious. Then execute a massive spearfishing attack.

Or use it as a hiring pool if you're an organization that is recruiting excellent code breakers.

Or just a really easy money laundering scheme.